1. Field of the Invention
The present invention relates to an improved technique for bonding a semiconductor chip to a conductive member such as a lead and a land pattern.
2. Description of the Prior Art
An apparatus 1 such as that shown in FIG. 1 is widely used to bond a semiconductor chip to a conductive lead by the TAB bonding method.
The apparatus 1 includes a pressure tool 7 which houses a heating mechanism, and a pedestal 6. Bonding using the apparatus 1 involves mounting a semiconductor chip 2 on the pedestal 6 and placing leads 4 on bumps 3 in registry therewith. A TAB tape TP is formed by an insulation tape 5 and the leads 4 adhered on the insulation tape 5. With the semiconductor chip 2 mounted on the pedestal 6 and the leads 4 registered onto the bumps 3, the heated pressure tool 7 pushes the leads 4 downwards. The heat of the pressure tool 7 flows to the bumps 3, thereby melting the bumps 3. The melted bumps 3 then cools down and hardens. As a result, the semiconductor chip 2 is bonded to the leads 4.
Although the bumps 3 are exaggerated regarding the thickness in FIG. 1, in reality, the bumps 3 are quite thin. Hence, when the semiconductor chip 2 is pushed downwards by the heated pressure tool 7, top surface of the semiconductor chip 2 is spaced from the bottom face of the pressure tool 7 by substantially no distance. Due to this, the conventional bonding process as above permits the heat of the tool 7 to be transferred in a considerable amount to the semiconductor chip 2 via the leads 4 and the bumps 3.
This in turn causes the temperature of the semiconductor chip 2 to jump up, which will deteriorate electrical and other characteristics of the semiconductor chip 2.
Further, bonding using the apparatus 1 of FIG. 1 requires that the semiconductor chip 2 is placed below the leads 4, i.e., in a face-up relation to the leads 4. This is because if the leads 4 are placed below the semiconductor chip 2, heat of the tool 7 will have to pass through the semiconductor chip 2 on the way to the bumps 3 and will inevitably cause an enormous increase in temperature of the semiconductor chip 2.
For the reason immediately above, it is not a practical choice to bond the semiconductor chip 2 with its bonding surface down, i.e., in the face-down style, by the apparatus 1 of FIG. 1.